1. Field of the Invention
The present invention relates to an aspirator fan particularly suitable for use in air-conditioners for motor vehicles.
2. Description of the Prior Art
Conventional aspirator fans of the type concerned include a rotor or impeller fixed on a rotating shaft which is supported by a pair bearings at its opposite ends. One example of such aspirator fans is disclosed in Japanese Utility Model Laid-open Publication No. 64-39118.
Since the rotating shaft is supported at its opposite ends as stated above, the two bearings must be accurately aligned with each other.
The bearings are firmly secured to a casing. As a consequence of this united or integral construction, when the casing is subjected to external forces or heat, central holes in the respective bearings are likely to displaced, thus hindering smooth rotation of the rotating shaft.
In order to prevent deformation of the casing, the casing must be formed of a highly rigid and thermally undeformable material. An alignment between the two bearings may be maintained by enlarging a clearance between the rotating shaft and the bearings. An enlarged clearance would, however, cause wobbling of the rotating shaft and the impeller, thus resulting in the generation of unpleasant noise.